202 THE POPULAR SCIENCE MONTHLY. 



neither, and if there is a fireplace it is generally closed up. Again, 

 it is a mistake to suppose that foul air goes to the top of a room. 

 Certainly the heated air goes to the top, but the chief impurity, the 

 carbonic acid, falls to the bottom. There is nothing so efficacious in 

 removing the lower strata of air as the ordinary open fireplace, es- 

 pecially if there is a fire burning. The usual defect in ventilation is 

 the want of a proper inlet for the air. If the window be open, the cold 

 air, being heavier, pours down into the room, causing draughts ; if the 

 door be open or ajar, the same thing occurs. The perfection of ventila- 

 tion may be obtained in any room with a fireplace by simply providing 

 proper inlets for the air, and nothing answers so well for the purpose as 

 the upright tubes invented by Mr. Tobin. By this means the heavier 

 external atmosphere ascends vertically through the tubes like the jet of a 

 fountain, displacing the warmer and lighter atmosphere of the room, 

 which finds its exit up the chimney. The tubes should communicate 

 with the outer air on a level with the floor, and should be carried ver- 

 tically upward in the room for about four or five feet. A constant 

 supply of fresh air is thus insured without the slightest liability to 

 draught, as the current goes directly upward until it strikes the 

 ceiling. It is then diffused downward, mixed with the heated air of 

 the ceiling. The same principle can be carried out in any room with 

 a sash-window, by cutting out two or three holes an inch wide and 

 three inches long in the wood-work of the upper sash where it joins 

 the lower one. The columns of air ascend directly upward, just inside 

 the window, and mix with the heated air in the upper part of the 

 room. If this system were universally carried out, we should hear 

 less of rheumatism and chills caught by sitting in draughts. 



9. Persons should cultivate the faculty of detecting sewer-gas in 

 houses. Typhoid fever is often caused by the escape of this gas into 

 the house through defect of the traps and drains. However bad the 

 drains may be outside of the house, there is little to fear, provided the 

 gas can escape externally. The following two very simple precau- 

 tions would naturally diminish the cases of typhoid fever: First, every 

 main drain should have a ventilating-pipe carried from it, directly 

 outside of the house, to the top of the highest chimney; secondly, the 

 soil-pipe inside the house should be carried up through the roof, and 

 be open at the top. English Mechanic. 



-+*+- 



CANINE SAGACITY. 



A CORRESPONDENT hands us the following anecdotes illustra- 

 tive of the remarkable reasoning powers of dogs : 

 The first case is one which occurred at a fashionable watering-place 

 on the east coast of Ireland, some twenty years ago, and exhibits the 

 remarkable sagacity displayed by a dog in carrying out the dictates 



